FIELD OF THE INVENTION
The invention relates to a device for protecting vehicle occupants in a motor vehicle.
International Publication No. WO 96/09942 A has an impact sensor which is located in a front area of a motor vehicle. A control unit is provided in a central area of the motor vehicle for controlling a vehicle occupant protection device. The impact sensor either has a plurality of mechanical acceleration switches which are sensitive to different accelerations and which supply a switching signal when a defined acceleration is exceeded. Alternatively an acceleration sensor which supplies an analog acceleration signal is provided as an impact sensor. The switching signals and/or the analog acceleration signal are supplied to the central control unit. The vehicle occupant protection device is triggered by the control unit if a signal of an acceleration sensor which is provided centrally with the control unit has a predefined profile, wherein this signal of the centrally located acceleration sensor is evaluated in a processor of the control unit. Individual operating states of the vehicle occupant protection device, such as individual stages of an airbag, for example, are subsequently selected as a function of the signal of the impact sensor.
When an electronic acceleration sensor is used as an impact sensor, interference variables acting on the line between the impact sensor and control unit can considerably falsify the sensitive analog signal which is supplied by the impact sensor. On the other hand, an extremely large amount of computational power has to be made available in the processor of the control unit to evaluate the analog signal. The need for such a large amount of computational power in the central processor is disadvantageous insofar as the processor has to cope with a large number of further computationally intensive functions such as evaluating signals of centrally disposed acceleration sensors or else also evaluating signals of other devices which are connected to the control unit, such as a device for detecting vehicle occupants and/or a child's seat. When mechanical acceleration switches are used as impact sensors, a relatively large signal-to-noise ratio is obtained when the switching signals are transmitted. However, such acceleration switches are complex components which are cost-intensive to manufacture and in particular do not permit precise evaluation of the timing of the acceleration acting on the front area of the vehicle.